U.S. patent number 7,930,037 [Application Number 10/846,329] was granted by the patent office on 2011-04-19 for field steerable electrical stimulation paddle, lead system, and medical device incorporating the same.
This patent grant is currently assigned to Medtronic, Inc.. Invention is credited to Kenneth T. Heruth, Mark Holle, James Skakoon.
United States Patent |
7,930,037 |
Heruth , et al. |
April 19, 2011 |
Field steerable electrical stimulation paddle, lead system, and
medical device incorporating the same
Abstract
An implantable electrode paddle is adapted to receive an
electrical signal from a medical device and generate an electrical
field to stimulate selected body tissue. The paddle includes a
housing including walls that define an interior space and a
plurality of windows formed through at least a first one of the
walls for transmitting the electrical field to the body tissue, an
electrode array including a plurality of electrode groups, each
electrode group including at least two electrodes individually
secured in a respective window and spaced between about 0.1 mm and
about 10 mm apart, and a plurality of wires, each of the wires
being coupled to a respective electrode and routed within the
interior space to receive the electrical signal. A lead assembly
and an implantable medical device can include the paddle.
Inventors: |
Heruth; Kenneth T. (Edina,
MN), Holle; Mark (Shoreview, MN), Skakoon; James (St.
Paul, MN) |
Assignee: |
Medtronic, Inc. (Minneapolis,
MN)
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Family
ID: |
34382016 |
Appl.
No.: |
10/846,329 |
Filed: |
May 14, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050070982 A1 |
Mar 31, 2005 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60507832 |
Oct 1, 2003 |
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60507389 |
Sep 30, 2003 |
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Current U.S.
Class: |
607/116;
607/117 |
Current CPC
Class: |
A61N
1/36071 (20130101); A61N 1/0553 (20130101); Y10T
29/49204 (20150115) |
Current International
Class: |
A61N
1/05 (20060101) |
Field of
Search: |
;607/46,43,118,115-117
;600/377 |
References Cited
[Referenced By]
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Other References
Karatas, A., S. Caglar, A. Savas, A. Elhan, and A. Erdogan.
"Microsurgical Anatomy of the Dorsal Cervical Rootlets and Dorsal
Root Entry Zones." Acta Neurochirurgica 147.2 (2005): 195-199. Nov.
19, 2007
<http://www.springerlink.com/content/qp81d2y5npaa4ehy/>.
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Primary Examiner: Bertram; Eric D.
Parent Case Text
This application claims the benefit of U.S. Provisional Application
No. 60/507,832, filed Oct. 1, 2003, and 60/507,389, filed Sep. 30,
2003 which are hereby incorporated herein by reference in their
entirety.
Claims
What is claimed is:
1. An implantable electrode paddle adapted to receive an electrical
signal from a medical device and generate an electrical field to
stimulate selected body tissue, the electrode paddle comprising: a
housing including walls that define an interior space and a
plurality of windows formed through at least a first one of the
walls for transmitting the electrical field to the body tissue, the
housing having a longitudinal dimension that is greater than a
lateral dimension of the housing; an electrode array including a
plurality of longitudinally spaced electrode groups with each
separated by a portion of the walls of the housing with
longitudinal spacing of the electrode groups being in a direction
of the longitudinal dimension of the housing, each electrode group
including at least two electrodes that are individually secured in
a respective window, that are immediately laterally adjacent, and
that are laterally spaced from closest edge to closest edge by an
amount that is less than the longitudinal spacing from closest edge
to closest edge between the electrode groups that are immediately
longitudinally adjacent, where the lateral spacing between the
immediately laterally adjacent electrodes from closest edge to
closest edge is between about 0.1 mm and less than 1 mm, and where
the lateral spacing from closest edge to closest edge between two
immediately adjacent electrodes of a first electrode group of the
plurality is the same as the lateral spacing from closest edge to
closest edge between two immediately adjacent electrodes of a
second electrode group of the plurality that is longitudinally
spaced from the first electrode group, with at least one electrode
of at least one electrode group having an applied common electrical
potential relative to an immediately laterally adjacent electrode
of the at least one electrode group; and a plurality of wires, each
of the wires being coupled to a respective electrode and routed
within the interior space to receive the electrical signal.
2. The implantable electrode paddle according to claim 1, wherein
the immediately laterally adjacent electrodes in each electrode
group are laterally spaced apart from closest edge to closest edge
by 0.5 mm.
3. The implantable electrode paddle according to claim 2, wherein
there are two electrode groups, each group consisting of eight
electrodes.
4. The implantable electrode paddle according to claim 1, further
comprising: an electronic network housed within the interior space
and adapted to receive the electrical signal and, in response
thereto, to select and transmit electrical pulses to one or more of
the electrodes.
5. The implantable electrode paddle according to claim 1, wherein
the electrodes within each group are evenly spaced apart.
6. An implantable lead system adapted to transmit an electrical
signal from a medical device and generate an electrical field to
stimulate selected body tissue, the system comprising: a first lead
body comprising at least one conductor; and an electrode paddle,
comprising: a housing including walls that define an interior space
and a plurality of windows formed through at least a first one of
the walls for transmitting the electrical field to the body tissue,
the housing having a longitudinal dimension that is greater than a
lateral dimension of the housing; an electrode array including a
plurality of longitudinally spaced electrode groups with
longitudinal spacing of the electrode groups being in a direction
of the longitudinal dimension of the housing, each electrode group
including at least two electrodes individually that are secured in
a respective window, that are immediately laterally adjacent, and
that are laterally spaced from closest edge to closest edge by an
amount that is less than the longitudinal spacing from closest edge
to closest edge between the electrode groups that are immediately
longitudinally adjacent, where the lateral spacing between the
immediately laterally adjacent electrodes from closest edge to
closest edge is between about 0.1 mm and less than 1 mm, and where
the lateral spacing from closest edge to closest edge between two
immediately adjacent electrodes of a first electrode group of the
plurality is the same as the lateral spacing from closest edge to
closest edge between two immediately adjacent electrodes of a
second electrode group of the plurality that is longitudinally
spaced from the first electrode group, with at least one electrode
of any one of the electrode groups having an applied common
electrical potential relative to an immediately laterally adjacent
electrode of the electrode group; and a plurality of wires, each of
the wires being routed within the interior space and coupled to a
respective electrode and to the first lead body.
7. The implantable lead system according to claim 6, further
comprising: a hermetic encasement, comprising: a housing defining
an interior space, an electronic network housed within the interior
space, a first set of one or more terminals electrically coupling
the electronic network to the electrode paddle, and a second set of
one or more terminals electrically coupling the electronic network
to the first lead body.
8. The implantable lead system according to claim 7, further
comprising: a second lead body comprising at least one conductor
having a first end that is electrically coupled to at least one of
the terminals in the first set, and a second end that is
electrically coupled to the electrode paddle.
9. The implantable lead system according to claim 6, wherein the
immediately laterally adjacent electrodes in each electrode group
are laterally spaced from closest edge to closest edge by 0.5
mm.
10. The implantable lead system according to claim 9, wherein there
are two electrode groups, each group consisting of eight
electrodes.
11. The implantable lead system according to claim 6, further
comprising: an electronic network housed within the interior space
and adapted to receive the electrical signal and, in response
thereto, to select and transmit electrical pulses to one or more of
the electrodes.
12. The implantable lead system according to claim 6, wherein the
electrodes within each group are evenly spaced apart.
13. An implantable medical device assembly for generating an
electrical field to stimulate selected body tissue, the device
comprising: a controlling device having an electrical output for
transmitting electrical signals; a first lead body comprising one
or more electrical conductors, the first lead body having a first
end and a second end, the first end being coupled to the electrical
output; and an electrode paddle, comprising: a housing including
walls that define an interior space and a plurality of windows
formed through at least a first one of the walls for transmitting
the electrical field to the body tissue, the housing having a
longitudinal dimension that is greater than a lateral dimension of
the housing; an electrode array including a plurality of
longitudinally spaced electrode groups separated by a portion of
the walls of the housing with longitudinal spacing of the electrode
groups being in a direction of the longitudinal dimension of the
housing, each electrode group including at least two electrodes
that are individually secured in a respective window, that are
immediately laterally adjacent, and that are laterally spaced from
closest edge to closest edge by an amount that is less than the
longitudinal spacing from closest edge to closest edge between the
electrode groups that are immediately longitudinally adjacent,
where the lateral spacing between the immediately adjacent
electrodes from closest edge to closest edge is between about 0.1
mm and less than 1 mm, and where the lateral spacing from closest
edge to closest edge between two immediately adjacent electrodes of
a first electrode group of the plurality is the same as the lateral
spacing from closest edge to closest edge between two immediately
adjacent electrodes of a second electrode group of the plurality
that is longitudinally spaced from the first electrode group, with
at least one electrode of at least one electrode group having an
applied common electrical potential relative to an immediately
laterally adjacent electrode of the at least one electrode group;
and a plurality of wires, each of the wires being routed within the
interior space and coupled to a respective electrode and to the
first lead body second end.
14. The assembly according to claim 13, wherein the controlling
device is an electrical pulse generator.
15. The assembly according to claim 14, wherein the electrical
pulse generator includes sixteen channels and sixteen electrical
outputs.
16. The assembly according to claim 13, wherein the controlling
device comprises: a receiver for wirelessly receiving external
instruction signals; and a processor coupled to the receiver and
adapted to produce the electrical signals in response to the
instruction signals.
17. The assembly according to claim 16, wherein the electrical
signals are pulse output commands, and the controlling device
further comprises: a memory that stores the pulse output
commands.
18. The assembly according to claim 13, further comprising: a
hermetic encasement, comprising: a housing defining an interior
space, an electronic network housed within the interior space, a
first set of one or more terminals electrically coupling the
electronic network to the electrode paddle, and a second set of one
or more terminals electrically coupling the electronic network to
the first lead body.
19. The assembly according to claim 18, further comprising: a
second lead body comprising at least one conductor having a first
end that is electrically coupled to at least one of the terminals
in the first set, and a second end that is electrically coupled to
the electrode paddle.
20. The assembly according to claim 13, wherein the immediately
laterally adjacent electrodes in each electrode group are laterally
spaced from closest edge to closest edge by 0.5 mm.
21. The assembly according to claim 20, wherein there are two
electrode groups, each group consisting of eight electrodes.
22. The assembly according to claim 13, further comprising: an
electronic network housed within the interior space and adapted to
receive the electrical signal and, in response thereto, to select
and transmit electrical pulses to one or more of the
electrodes.
23. The assembly according to claim 13, wherein the electrodes
within each group are evenly spaced apart.
24. An implantable electrode paddle adapted to receive an
electrical signal from a medical device and generate an electrical
field to stimulate selected body tissue, the electrode paddle
comprising: a housing including walls that define an interior space
and a plurality of windows formed through at least a first one of
the walls for transmitting the electrical field to the body tissue;
an electrode array including a plurality of longitudinally spaced
electrode groups with each separated by a portion of the walls of
the housing, each electrode group including at least two electrodes
that are individually secured in a respective window, that are
immediately laterally adjacent, and that are laterally spaced from
closest edge to closest edge by an amount that is less than the
longitudinal spacing from closest edge to closest edge between the
electrode groups that are immediately longitudinally adjacent,
where the lateral spacing between the immediately laterally
adjacent electrodes from closest edge to closest edge is between
about 0.1 mm and less than 1 mm, and where the lateral spacing from
closest edge to closest edge between two immediately adjacent
electrodes of a first electrode group of the plurality is the same
as the lateral spacing from closest edge to closest edge between
two immediately adjacent electrodes of a second electrode group of
the plurality that is longitudinally spaced from the first
electrode group, with at least one electrode of at least one
electrode group having an applied common electrical potential
relative to an immediately laterally adjacent electrode of the at
least one electrode group, with at least one of the electrode
groups including only a single laterally spaced row of the at least
two electrodes; and a plurality of wires, each of the wires being
coupled to a respective electrode and routed within the interior
space to receive the electrical signal.
25. An implantable electrode paddle adapted to receive an
electrical signal from a medical device and generate an electrical
field to stimulate selected body tissue, the electrode paddle
comprising: a housing including walls that define an interior space
and a plurality of windows formed through at least a first one of
the walls for transmitting the electrical field to the body tissue;
an electrode array including a plurality of longitudinally spaced
electrode groups with each separated by a portion of the walls of
the housing, each electrode group including at least two electrodes
that are individually secured in a respective window, that are
immediately laterally adjacent, and that are laterally spaced from
closest edge to closest edge by an amount that is less than the
longitudinal spacing from closest edge to closest edge between the
electrode groups that are immediately longitudinally adjacent,
where the lateral spacing between the immediately laterally
adjacent electrodes from closest edge to closest edge is between
about 0.1 mm and less than 1 mm, and where the lateral spacing from
closest edge to closest edge between two immediately adjacent
electrodes of a first electrode group of the plurality is the same
as the lateral spacing from closest edge to closest edge between
two immediately adjacent electrodes of a second electrode group of
the plurality that is longitudinally spaced from the first
electrode group, with at least one electrode of at least one
electrode group having an applied common electrical potential
relative to an immediately laterally adjacent electrode of the at
least one electrode group, with at least one electrode group
including at least one electrode that has a longitudinal dimension
that is at least three times as large as a lateral dimension; and a
plurality of wires, each of the wires being coupled to a respective
electrode and routed within the interior space to receive the
electrical signal.
Description
TECHNICAL FIELD
The present invention generally relates to medical leads for
biological tissue therapy, and more particularly relates to systems
and methods for steering a tissue stimulating electrical field
using implantable medical leads.
BACKGROUND
Dorsal columns are long myelinated fibers oriented along the spinal
cord axis and centrally located around the lumbar spine between the
dorsal roots. Researchers have found that fibers enter the dorsal
horn, and are arranged in approximately v-shaped layers. Fibers
that enter at a higher vertebral level form a v-shaped layer
covering the layers that originated at lower levels. The nerve
fiber organization is less structured below the dorsal column
surface, where the fibers are two or more vertebral levels away
from their point of entry. M. C. Smith et al., Topographical
Anatomy of the Posterior Columns of the Spinal Cord in Man, 107
Brain 671 (1984). FIG. 1 is a cross sectional view of different
vertebra through the spinal cord with symbols illustrating the
spinal nerve pathways through the dorsal column.
Chronic pain originating in the lower back is quite common. Spinal
cord stimulation is an accepted therapy for chronic pain. However,
physicians have found that it can be difficult to properly position
the spinal cord stimulation lead to achieve good pain relief for
lower back pain. As illustrated in FIG. 1, nerve fibers associated
with lower back pain (S4 to L5), are only close to the dorsal
column surface for a short distance and are consequently difficult
to locate. Physicians who consider properly treating lower back
pain with SCS must develop an effective SCS technique and must
learn to manipulate a stimulating lead with unusual skill and
patience. Such a technique often involves implanting a stimulating
device and carefully positioning at least one stimulating lead into
a patient's spinal area. Even if the technique is performed
properly, the leads may need to be repositioned over time.
Repositioning the stimulating leads is typically an invasive
surgical procedure that carries risks and requires great patience,
care, and skill.
Accordingly, it is desirable to provide a system and method that
physicians can readily adopt for stimulating the spinal cord,
particularly areas of the spinal cord that have low surface
concentrations of readily manipulated nerves such as those in the
dorsal columns. In addition, it is desirable to provide a system
and method for non-invasively relocating an electrical field after
the system is implanted. Furthermore, other desirable features and
characteristics of the present invention will become apparent from
the subsequent detailed description and the appended claims, taken
in conjunction with the accompanying drawings and the foregoing
technical field and background.
BRIEF SUMMARY
An implantable electrode paddle is provided for receiving an
electrical signal from a medical device and generating an
electrical field to stimulate selected body tissue. The electrode
paddle comprises a housing including walls that define an interior
space and a plurality of windows formed through at least a first
one of the walls for transmitting the electrical field to the body
tissue, an electrode array including a plurality of electrode
groups, each electrode group including at least two electrodes
individually secured in a respective window and spaced between
about 0.1 mm and about 10 mm apart, and a plurality of wires, each
of the wires being coupled to a respective electrode and routed
within the interior space to receive the electrical signal.
An implantable lead system is provided to transmit an electrical
signal from a medical device and generate an electrical field to
stimulate selected body tissue. The system comprises a first lead
body comprising at least one conductor, and the electrode paddle
described above.
An implantable medical device is also provided for generating an
electrical field to stimulate selected body tissue. The device
comprises a controlling device such as an electrical pulse
generator having an electrical output for transmitting electrical
signals, and the lead body and electrode paddle described
above.
A method is provided for manufacturing an implantable electrode
paddle that is adapted to receive an electrical signal from a
medical device and generate an electrical field to stimulate
selected body tissue. The method comprises the step of assembling
an electrode array including a plurality of electrode groups, and a
plurality of wires coupled to the electrode array, onto a first
insulative substrate having a plurality of windows formed
therethrough for transmitting the electrical field to the body
tissue, and securing each electrode in a respective window with the
electrodes in each group spaced between about 0.1 mm and about 10
mm apart.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will hereinafter be described in conjunction
with the following drawing figures, wherein like numerals denote
like elements, and
FIG. 1 is a cross sectional view of different vertebra through the
spinal cord with symbols illustrating the spinal nerve pathways
through the dorsal column;
FIG. 2 is an illustration of a patient with an implantable pulse
generator implanted in the patient's abdomen and a lead connected
to the pulse generator placed in the epidural space next to the
spinal cord according to an embodiment of the present
invention;
FIG. 3 is a top view of an exemplary electrode paddle 30 according
to an embodiment of the present invention;
FIG. 4 is a top view of a medical device assembly including an
implantable pulse generator, a first lead body portion, an in-line
hermetic encasement, and a second lead body portion that are
electrically connected in sequence according to an embodiment of
the present invention;
FIG. 5 is an exploded view of the hermetic electronic encasement
depicted in FIG. 4;
FIGS. 6 to 9 are images from a computer model of electrical fields,
illustrating the effect of selecting different electrodes to supply
stimulation to the spinal cord according to an embodiment of the
present invention;
FIG. 10 is an exploded view of a substrate and wire-electrode
assemblies to be mounted thereon to manufacture an electrode paddle
according to an embodiment of the present invention;
FIG. 11 is an exploded view of substrate sheets securing electrodes
and routing wires to manufacture an electrode paddle according to
an embodiment of the present invention;
FIG. 12 is an isometric view of the substrate sheets depicted in
FIG. 11 being fit into a boot to manufacture an electrode paddle
according to an embodiment of the present invention.
DETAILED DESCRIPTION
The following detailed description is merely exemplary in nature
and is not intended to limit the invention or the application and
uses of the invention. Furthermore, there is no intention to be
bound by any expressed or implied theory presented in the preceding
technical field, background, brief summary or the following
detailed description.
While the following description is generally directed to treatments
and systems involving a neurological stimulator in the form of an
implantable pulse generator, the utility of the apparatus and
method of the present invention is not limited to neurostimulatory
pulse generating devices and can be adapted for use with a variety
of implantable electrical devices that use multiple electrical
leads to send electrical pulses to selected body parts. FIG. 2 is
an illustration of a patient 110 with an implantable pulse
generator (IPG) 10 implanted in the patient's abdomen. The IPG 10
transmits independent stimulation pulses to the spinal cord 120
using an insulated lead 12 and electrodes 32 coupled thereto. The
lead 12 is routed around the flank toward the spinal column 120,
and the electrodes 32 are placed in the epidural space next to the
spinal column 120. An extension (not shown), including a conductor,
may also be used to electrically connect the IPG 10 to the lead
12.
In order to manipulate the location of the electrical field
produced by the electrodes 32, the IPG 10 includes a plurality of
outlets as necessary to selectively and independently control each
electrode 32 to which the IPG 10 is coupled. According to one
exemplary embodiment, the IPG 10 includes sixteen channels and
respective outlets to control a field steerable stimulation lead
including sixteen electrodes. In an alternative exemplary
embodiment, the IPG 10 has fewer independent channels and
respective outlets than the number of leads controlled thereby, and
transmits coded address signals before each stimulation pulse to
instruct which of the electrodes will transmit pulses to a patient.
Electronics are disposed downstream from the IPG 10 on the lead to
receive the coded address signals and, responsive thereto, to
select and control the electrodes indicated by the coded
signals.
The IPG 10 and the associated system typically utilize fully
implantable elements, although it is within the scope of the
invention to utilize partially implanted generators that employ
wireless coupling technology such as electronic components sold by
Medtronic, Inc. under the trademarks X-trel.TM. and Mattrix.TM.. A
wireless receiver in the IPG 10 can be adapted to receive
instruction commands from a physician or another user, the
instruction commands selecting stored pulse output commands from
the IPG 10 or programming new pulse output commands. Also,
according to either of the exemplary embodiments described above,
the IPG 10 includes a memory for storing pulse output commands that
can be programmed in advance of implantation and are tailored to a
patient's needs. The output commands can be transmitted directly to
the selected electrodes. In another embodiment, the output commands
are encoded in address signals that are transmitted to a downstream
electronic network that decodes and generates pulse output commands
and transmits them to selected electrodes. The electrodes can be
programmed individually, or controlling programs can generate
commands that are transmitted to predetermined groups of electrodes
depending on the patient's needs.
After the IPG 10 is implanted, the pre-programmed pulse output
commands can be modified using an external programmer 40 that
communicates wirelessly with the IPG 10. The programmer 40 is
equipped with an antenna 41 for wireless communication, and the IPG
10 is equipped with a receiver (not shown). The programmer 40 can
communicate using any suitable known communication signals
including but not limited to radio frequency signals. Wireless
communication with the IPG 10 enables a physician or the patient to
non-invasively relocate the electrical field after the IPG 10 is
implanted, and to thereby adjust the dorsal column stimulation.
Because specific fibers on the dorsal column can be electrically
stimulated or not stimulated through post-surgical manipulation,
the intricacy of implanting the IPG leads and electrodes 32 is
substantially reduced. The physician performing the surgery can
implant a lead body that houses the IPG electrodes 32 in a general
area on the dorsal column and then later steer or alter the
electrical field using the programmer 40.
In a general sense, manipulating and adjusting the excitation locus
can be performed using known techniques. Although the present
invention is directed to fine tuning tissue stimulation, general
techniques such as those described in U.S. Pat. No. 5,713,922,
incorporated herein by reference, for neural tissue excitation
adjustment in the spinal cord or brain can be used in combination
with the present invention.
Steering or altering the IPG electrical field is further enabled
according to the present invention by a fine tuning apparatus that
secures and distributes the stimulating electrodes in the dorsal
column vicinity. FIG. 3 is a top view of an exemplary electrode
paddle 30. The electrode paddle 30 provides a hermetic encasement
for circuitry and electronics, and also secures and supports many
small and closely spaced electrodes 32. The electrode paddle 30 and
the electrodes 32 exposed thereon are formed using biostable
materials, and the electrodes 32 are secured in the housing in a
manner whereby corrosive body fluids are unable to contaminate the
paddle interior and corrode or otherwise disrupt the electrode
circuitry 32. The electrode paddle 30 organizes the electrodes 32
into one or more groups 31, and in an exemplary embodiment the
electrodes 32 are organized into at least two groups 31. The
intra-group and inter-group electrode distribution on the electrode
paddle 30 prevents the electrodes from contacting one another, and
at the same time creates a dense electrode region 33. The dense
electrode region 33 permits the electrode paddle 30 to be small
despite the large number of electrodes 32 secured thereon, and
therefore to be positionable in the dorsal column vicinity with
minimal impact on body tissues.
The exemplary electrode paddle 30 in FIG. 3 includes two electrode
groups 31, with eight electrodes 32 in each group 31. The groups 31
are spaced apart in the longitudinal direction A of the electrode
paddle 30, and the electrodes 32 within each group 30 are spaced
apart in the lateral direction B. Although the number of electrodes
and their precise configuration on the electrode paddle 30 can vary
without varying from the scope of the present invention, the
configuration illustrated in FIG. 3 provides closely-spaced
electrodes 32 that can be individually controlled to steer the
electrical field that is therapeutically provided to a patient. In
an exemplary embodiment the electrodes are each about 0.5 mm wide
and are consistently spaced about 0.5 mm apart, although other
electrode sizes and spacing may be suitable. For example, the
electrodes can be spaced between about 0.1 mm and about 10 mm
apart, and are preferably spaced between about 0.1 mm and about 0.5
mm apart.
When two electrodes are spaced about 0.5 mm apart, switching the
electrical pulses from one electrode to the nearest laterally
adjacent electrode laterally shifts the electrical field center
about 0.5 mm. For an even more precise shift and a higher current,
both of the two adjacent electrodes can be selected, causing the
electrical field to be centered between the two electrodes and to
have a larger current. Also, in some cases a high current may
required to effectively stimulate a desired nerve fiber, and the
voltage capability of the IPG 10 may be exceeded. The electrodes 32
are so closely spaced on the electrode paddle 30 that two or more
electrodes 32 may be selected simultaneously to effectively
function as a single larger electrode. With the electrode paddle 30
implanted in the dorsal column vicinity, selected nerve fibers can
be carefully and precisely stimulated by steering the electrical
field between the electrodes 32 in this manner.
The electrode paddle 30 can be used in combination with other known
voltage divider systems as appropriate. U.S. Pat. Nos. 5,501,703
and 5,643,330, and Publication WO 95/19804, are incorporated herein
in by reference. These references disclose, inter alia, an electric
field steering process that involves individually controlling the
voltage at each of a plurality of electrodes. More particularly,
the references disclose individually manipulating the voltage of at
least three electrodes that are incorporated in a multichannel
apparatus for epidural spinal cord stimulation.
In an exemplary embodiment of the invention, electronics are
provided on the lead between the electrode paddle 30 and the IPG
10. A coded signal is sent from the IPG 10 to an electronics
package that selectively activates the electrodes 32 in response.
FIG. 4 is a top view of a medical device assembly including the IPG
10, a first lead body portion 12a, an in-line hermetic encasement
20, and a second lead body portion 12b that are electrically
connected in sequence. Each lead body 12a, 12b may include one or
more leads that may be combined in one or more lead bodies. When
the assembly is implanted, the first lead body portion 12a is
electrically coupled to the IPG 10, and extends to another suitable
location in the patient's body where it is electrically coupled to
a hermetic electronic encasement 20. The encasement 20 houses an
electronic network that may include a memory for storing programs
that, when carried out, enable the electronic network to
communicate with and control multiple electrodes disposed on the
electrode paddle 30. The encasement 20 may further include at least
one energy source such as a battery to power the electronic network
and the electrode paddle 30. An exemplary embodiment of the
encasement 20 and its contents will be described in greater detail
below.
A plurality of leads collectively identified as the lead body
portion 12b are electrically coupled to the encasement 20 at one
end and are directly engaged or indirectly coupled with the
electrode paddle 30 at an opposite end. Optionally, a connector
block 22 can be fastened to the encasement 20. The connector block
22 electrically connects one or more leads to the encasement 20 via
connectors such as lead clamps (not shown) that hold the leads in
place.
FIG. 5 is an exploded view of a hermetic electronic encasement 20
disclosed in U.S. patent application Ser. No. 10/742,732 which is
incorporated herein by reference. As mentioned above, the
encasement 20 serves as the housing for electronic intelligence and
other components such as at least one energy source 21, and
integrated electrical circuitry/components 19. The encasement 20 is
in-line with the lead body 12a, 12b and consequently enables the
electrode paddle 30 and, optionally, other stand-alone devices or
components that may be controlled by the IPG 10 to be disposed
downstream from and in direct communication with the IPG 10.
Although the energy source 21 may be a simple battery, the hermetic
encasement 20 may be powered by dedicated conductive lines from the
IPG 10. In another embodiment, the energy source 21 harvests or
rectifies power from the IPG 10 stimulation pulses and stores the
same in order to power the hermetic encasement 20 and the electrode
paddle 30. In yet another embodiment, the hermetic encasement 20 is
temporarily powered via an external magnetic field or RF
energy.
The electrical circuitry/components 19 are integrated into or
mounted onto a multi-layered circuit board 17 formed of biostable
materials. In an exemplary embodiment of the invention the circuit
board 17 is a multi-layered ceramic structure that includes surface
bonding pads 18 for coupling the circuitry/components 19 to the
lead body 12a, 12b. The bonding pads 18 are deposited onto the
circuit board 17 using any conventional depositing method and are
formed from a biocompatible metal such as gold or platinum.
Examples of depositing techniques include printing, chemical vapor
deposition, or physical deposition such as sputtering.
The encasement assembly can include side walls 15 that combine to
surround the mid-portion of the circuit board 17, and end walls 16
that are attached to the side walls 15 to complete the encasement
20. In an exemplary embodiment of the invention, the end walls 16
and side walls 15 are composed of a ceramic material. In order to
protect and maintain the connections between the bonding pads 18
and the lead body 12a, 12b a flexible strain relief device 14 can
be attached to one or both of the encasement ends. An adaptor 13
can be coupled to the strain relief device 14 to appropriately
shape the device 14 and provide rigidity to the portion of the
device 14 that interfaces with an endplate 16.
In another exemplary embodiment of the invention, an integrated
lead system is employed in which electronics are provided on the
electrode paddle 30, or on another lead extension in communication
with the electrode paddle 30, to allow use of large numbers of
electrodes with a small number of conductors extending along the
lead wire and/or extension. A coded signal is provided to the
electrode paddle 30 from the IPG, and the electrode paddle
electronics identify which electrodes to activate in response
thereto. More particularly, the electronics on the electrode paddle
30 include a controller that responds to the coded signal and
selectively activates the electrodes 32. The electronics may be
included within the paddle housing or may be separately housed
adjacent to the electrode paddle 30. The embodiments described
above or within the scope of the invention as described herein can
be used in combination with additional known electronics for
selecting and controlling electrode arrays. See, for example, U.S.
Pat. No. 6,038,480 (Hrdlicka et al) on living tissue stimulation
and recording techniques with local control of active sites; U.S.
Pat. No. 6,473,653 (Schallhom et al) on selective activation of
electrodes within an implantable lead, and US Patent Application
Publication No. US2003/0093130A and PCT Patent Publication No.
WO2003/041795A (Stypulkowski) on multiplexed electrode array
extensions, all three of which are incorporated herein by reference
in their entirety.
Returning now to the functional aspects of the invention, FIGS. 6
to 9 are images from a computer model of electrical fields,
illustrating the effect of selecting different electrodes to supply
stimulation to the spinal cord. More particularly, the figures
illustrate the result of a computer modeling study of the
electrical field generated by an electrode. Each figure is a cross
section of the spinal cord 120, with an eight-electrode paddle 30
located in the epidural space. The eight electrodes 32 are
designated as electrodes 32a, 32b, 32c, 32d, 32e, 32f, 32g, and 32h
progressing upwardly from left to right with electrode 32a on the
far left. The electrode-generated electrical field is steerable
about the spinal cord 120 as different electrodes 32 are selected.
In the figures, the electrodes 32 are spaced 0.5 mm apart, although
such spacing is merely exemplary and can be adjusted depending on
the patient's needs. In FIG. 6, electrode 32e is selected,
generating an electrical field 35e about a spinal cord area. In
FIG. 7, electrode 32f is selected and the electrical field 35f
changes its shape and position to stimulate a different spinal cord
area. The fields 35g, 35h are shown in FIGS. 8 to 9, respectively,
as electrodes 32g and 32h are selected.
Exemplary methods for manufacturing the electrode paddle 30 will
now be discussed. FIG. 10 is an exploded view of a substrate 36 and
wire-electrode assemblies to be mounted thereon. The individual
electrodes 32 are formed from any suitable conductive metal such as
platinum-iridium. The wire-electrode subassemblies are then
individually assembled onto a substrate 36 that includes a window
37 for each electrode 32 that exposes the electrode 32 to the
spinal cord. The substrate 36 is typically polyurethane, but can be
formed from a fiberglass, a polyimide, a thermoset elastomer such
as silicone, another suitable polymer such as an injection molded
polymer, or another suitable nonconductive material. The
wire-electrode subassemblies are assembled onto the substrate 36 by
a suitable technique. Alternatively, the electrodes 32 may be
directly deposited onto the substrate 36 using a deposition
process, or an etching process using a completely metallized
surface as a starting material. One of the above processes is
typically performed to first deposit or otherwise assemble the
electrodes 32, and thereafter form the wires 34 and join them to
the electrodes 32 using a laser welding method, a crimping method,
or other suitable joining process. Although not shown in FIG. 10,
an insulative backing substrate may be adhered or otherwise joined
to or be integral with the substrate 36 to shield and further
isolate the electrodes 32 and wires 34 from the external
environment and from each other.
In an exemplary embodiment, the substrate 36 includes two sheets
36a, 36b. FIG. 11 is an exploded view of the substrate sheets 36a,
36b securing the electrodes 32 and routing the wires 34. The sheets
36a, 36b are made from a resin such as polyurethane, or another
suitable material as recited above. The electrode/wire assemblies
are coupled using a process selected from those processes recited
above, and are placed in slots 37 in sheet 36a. The electrodes 32
may be temporarily retained using adhesive or a heated probe to
melt small amounts of polyurethane over each electrode 32. The
other polyurethane sheet 36b is then placed on top of the first
sheet 36a and the electrode/wire assemblies, trapping the wires and
electrodes. Adhesive or heat staking may be used to temporarily
retain the electrodes 32 and wires 24 for handling. The entire
assembly 36 is then placed in a hot fixture, and a hot plate
presses the sheets 36a, 36b. The heat allows the softened
polyurethane to flow about any open spaces to encapsulate the
electrode/wire assemblies and seal the sheets together with a
fluid-impermeable seal.
FIG. 12 is an isometric view of the substrate 36 being fit into a
boot 38. The boot 38 is made of silicone, polyurethane, or other
suitable nonconductive material, and includes a receiving slot 39
in which the substrate 36 is received and then slidingly engaged.
The slot 39 is of a depth that causes the top surface of sheet 36a
to be flush with the top surface of the boot 38, and is sized to
expose the electrodes 32 to the spinal cord to the boot exterior.
Thus, the paddle 30 can be implanted with the electrodes 32
uniformly distanced from the spinal cord. After the substrate 36 is
secured in the boot 38, the wires 34 are routed into a connection
tube 40 and joined to one or more lead bodies 12. Adhesives such as
silicone RTV or other sealants may be used to fill in any holes or
to secure any panels that were installed during the manufacturing
process.
While at least one exemplary embodiment has been presented in the
foregoing detailed description, it should be appreciated that a
vast number of variations exist. It should also be appreciated that
the exemplary embodiment or exemplary embodiments are only
examples, and are not intended to limit the scope, applicability,
or configuration of the invention in any way. Rather, the foregoing
detailed description will provide those skilled in the art with a
convenient road map for implementing the exemplary embodiment or
exemplary embodiments. It should be understood that various changes
can be made in the function and arrangement of elements without
departing from the scope of the invention as set forth in the
appended claims and the legal equivalents thereof.
* * * * *
References